This is first of four projects investigating the clinical pharmacology of the indirectly acting sympathomimetic psychostimulant methamphetamine and its enantiomers. The experiment will evaluate pharmacokinetic and dynamic interactions of racemic and optically pure methamphetamine on metabolic, cardiovascular, and subjective effects using enantiomer-specific assays. Despite a large literature on methamphetamine pharmacology in animals, there are relatively few studies comparing the stereoisomers in humans using modern pharmacokinetic/pharmacodynamic techniques. Understanding the differences in the pharmacology of stereoisomers is essential in understanding the pharmacology and toxicology of methamphetamine abuse, and may even be valuable in developing new treatment strategies. The services provided by the GCRC are vital to the successful completion of this study. To ensure subject compliance and safety, we will require inpatient hospitalization from the day before dosing through 48 hours postdosing for each of six separate admissions. Some of the services we will need from the GCRC include clinical admitting procedures; placement of IV catheters; monitoring vital signs at specified times; and collecting, processing, and packaging study-mandated urine and blood samples.